The invention concerns a method for producing metal strip by direct strand reduction, in which a thin slab is first cast in a casting machine and then rolled in at least one rolling train with utilization of the primary heat of the casting process. The invention also concerns an installation for producing metal strip by direct strand reduction.
Installations of this type are known as thin slab-thin strip direct strand reduction installations and are referred to as CSP installations.
Continuous rolling from the casting heat has long been known but has not yet found commercial success. The rigid connection of the continuous casting installation and the rolling train and temperature control through the whole installation have proven difficult to control.
EP 0 286 862 A1 and EP 0 771 596 B1 disclose methods and installations for continuous rolling from the casting heat. In these cases, the casting process and the rolling process are directly coupled. The continuous strip is cut with a shear shortly before the coiler.
EP 0 415 987 B2 and EP 0 889 762 B1 disclose similar methods for the continuous production of strip steel with the coupling of casting and rolling installations. To overcome the temperature problems at the relatively low conveyance speed, inductive heating units are provided upstream of and within the rolling train.
An alternative technology to this is the rolling of single slabs and single strips. In the discontinuous rolling of strip, the casting and rolling are disconnected from each other. The casting speed is usually very low, and the rolling speed is at a high level and independent of the casting speed, such that the temperature for the last deformation is above the minimum temperature. Installations of this type, which are also referred to as CSP installations, are described, for example, in EP 0 266 564 B1, in which a high reduction is carried out in the thin slab installation.
EP 0 666 122 A1 describes a similar thin slab installation, in which discontinuous strips are rolled with the use of inductive heating between the first finishing stands.
The advantages of discontinuous rolling are that the casting and rolling speed can be adjusted independently of each other. In thin strip rolling, higher rolling speeds can be adjusted, e.g., flexibly, even when the casting installation operates at a lower speed or the speed is just then being adjusted there.
Both methods, i.e., on the one hand, continuous casting and rolling and, on the other hand, discontinuous casting and rolling, are difficult to combine due to the circumstances described above.